Engines (heat engines) that convert heat energy into mechanical energy include internal combustion engines such as gasoline engine and diesel engine, and external combustion engines such as steam engine that executes the so-called Rankine cycle. The internal combustion engine intermittently burns the fuel in the air which is an operation fluid and converts the generated heat into mechanical energy. On the other hand, the steam engine which is an external combustion engine transfers the heat generated by the continuous combustion to the operation fluid offering such advantages that it is easy to control the burning state of the fuel and that harmful exhaust components due to the burning, such as NOx, CO, etc. are formed in small amounts. Besides, the external combustion engine can use not only the heat of combustion but also a variety of kinds of heat sources such as exhausted heat by the internal combustion engine, etc., and has excellent features such as saving energy and also from the standpoint of coping with the environment.
To utilize the above features of the steam engine, study and development have been forwarded to employ the steam engine for vehicles. For instance, JP-A-2002-115506 is disclosing a Rankine cycle unit which actuates the steam engine by using, as a source of heat, the exhausted heat from an internal combustion engine to recover the exhausted heat as mechanical energy. The steam engine unit for executing the Rankine cycle is constituted by a boiler (evaporator) for heating the operation fluid such as water, an expansion machine (steam engine) for generating power by expanding the operation fluid that is heated at a high temperature to have a high pressure, a condenser for cooling and liquefying the operation fluid after it has expanded and a circulating pump for pumping the liquefied operation fluid to the boiler. A turbine is, usually, used as the expansion machine.
The turbine which is a steam engine is a so-called velocity-type engine that utilizes velocity energy, and is equipped with many blades on which the steam of a high speed acts. To efficiently operate the turbine, it is necessary to increase the rotational speed of the turbine so that the peripheral speed of the blades increases to a value that meets the velocity of the steam. Therefore, the turbine becomes a complex engine that operates at high speeds. Besides, the steam engine unit is provided with a boiler, a condenser and the like; i.e., the steam engine unit tends to become a facility which is large in scale.
Under such circumstances, the present applicant has developed a compact steam engine unit that efficiently operates even at low speeds as disclosed in JP-A-2006-329036. According to this steam engine unit as shown in FIG. 4, a rotor 103 having a bent jet pipe 102 is rotatably supported in a closed container 101 filled with the operation fluid in a liquid state. The rotor 103 is provided with an intake pipe 104, and a heating unit 105 is inserted in a central cylinder at the center of the rotor to thereby constitute a boiler. The operation fluid in the liquid state taken in through the intake pipe 104 is vaporized in the heating portion 105 to produce a steam which is jetted from the jet pipe 102 in a state of being mixed with the liquid to rotate the rotor 105 clockwise. The jetted steam is guided into a condenser 106 installed over the closed container 101, and is condensed and is refluxed into the closed container 101. In order to control the jet and intake of the operation fluid, a jet check valve 107 and an intake check valve 108 are disposed at the end portions of the jet pipe 102 and the intake pipe 104, respectively.
In the steam engine of FIG. 4, the rotor having the jet pipe is provided in the closed container filled with the liquid, the steam of a high pressure vaporized by the heating unit at the center of the rotor is jetted from the jet pipe in the state of a mixture of the liquid and the steam, and the rotational force is obtained by the reaction thereof. The jetted mixture contains much liquid and its mass is far greater than that of the steam. Therefore, the rotational torque of the rotor becomes very larger than that of the case of when the steam only is jetted. Accordingly, a large torque is obtained even when the rotor rotates at low speeds and, hence, the steam engine can be efficiently operated even at low speeds. Besides, the boiler and the condenser are fabricated integrally with the closed container, and the steam engine unit as a whole is compact in size.
Patent document 1: JP-A-2002-115506
Patent document 2: JP-A-2006-329036